U.S. patent number 3,925,140 [Application Number 05/341,850] was granted by the patent office on 1975-12-09 for fabricating apparatus for twin-sheets.
This patent grant is currently assigned to Koehring Company. Invention is credited to Gaylord W. Brown.
United States Patent |
3,925,140 |
Brown |
December 9, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Fabricating apparatus for twin-sheets
Abstract
Apparatus and methods for fabricating a hollow plastic object
from a pair of heat-fusible, thermoplastic sheets which are
serially moved in a common horizontal plane from a heating station
to a mold mechanism at a forming station. At the forming station,
one of the sheets is received by a mold which is then moved
vertically to move the sheet out of the plane to a position
juxtaposed with a following sheet when the latter arrives at the
forming station. At least one of the sheets is differential
pressure molded after arrival at the forming station and the sheets
are then vertically moved together and fused to form the
object.
Inventors: |
Brown; Gaylord W. (Beaverton,
MI) |
Assignee: |
Koehring Company (Milwaukee,
WI)
|
Family
ID: |
23339270 |
Appl.
No.: |
05/341,850 |
Filed: |
March 16, 1973 |
Current U.S.
Class: |
156/382; 156/359;
425/383; 156/499 |
Current CPC
Class: |
B29C
51/267 (20130101); B29C 66/8322 (20130101); B29C
66/82421 (20130101); B29C 65/02 (20130101); B29C
65/18 (20130101); B29C 66/54 (20130101) |
Current International
Class: |
B29C
65/00 (20060101); B29C 69/00 (20060101); B29C
65/18 (20060101); B32B 031/26 () |
Field of
Search: |
;156/285,382,362,363,364,366,499,500,358,359
;425/185,383,384,388,156 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Weston; Caleb
Claims
What is claimed is:
1. Apparatus for forming hollow objects from first and second
thermoplastic sheets wherein the amount of heat required to bring a
first sheet to its forming temperature differs substatially from
the amount of heat required to bring a second sheet to its forming
temperature, said apparatus comprising heating means, diferential
pressure, mold forming means located at a forming station adjacent
said heating means, carrier means for advancing first and second
sheets in uniformly spaced alternate succession in intermittent
step-by-step movement along a fixed path with each first sheet
being located one step in advance of a second sheet, said carrier
means carrying said sheets in succession into operative
relationship with said heating means and subsequently advancing
said sheets in succession into operative relationship with said
forming means at said forming station while pausing for a
predetermined time interval between successive steps of movement to
accommodate heating and forming of said sheets while said sheets
are at said heating means and forming station, means at said
forming station operable on alternate steps of movement of said
carrier means to transfer a first sheet from said carrier means to
said forming means within said predetermined time interval between
a first step of movement of said carrier means and its next step of
movement and operable after said next step of movement of said
carrier means advances a second sheet into operative relationship
with said forming means to actuate said forming means to form said
object within the predetermined time interval between said next
step of movement and the next subsequent step of movement, and
first heater control means responsive to the arrival of a first
sheet at said heating means for operating said heating means to
supply a first amount of heat to said first sheet within said
predetermined time interval and responsive to the arrival of a
second sheet at said heating means for operating said heating means
to supply a second amount of heat, differing from said first amount
of heat, to said second sheet within said predetermined time
interval.
2. Apparatus as defined in claim 1 wherein said heating means
comprises a first and a second heater at said heating station
spaced along said fixed path by a distance corresponding to the
length of one step of movement of said carrier means whereby a
sheet on said carrier means is located in operative relationship
with said first heater at the conclusion of one step of movement of
said carrier means and in operative relationship with said second
heater at the conclusion of the next successive stop of movement of
said carrier means, said heater control means controlling operation
of said first heater, and second heater control means for operating
said second heater to supply equal amounts of heat to first and
second sheets advanced into operative relationship therewith.
3. Apparatus as defined in claim 1 wherein said forming station is
spaced from said second heater by a distance corresponding to one
step of movement of said carrier means and said second control
means operates said second heater to maintain a substantially
constant termperature in the region occupied by sheets in operative
relationship with said second heater.
Description
BACKGROUND OF THE INVENTION
This invention relates to differential pressure forming methods and
apparatus, and more particularly to an apparatus for, and a method
of, forming a hollow object in a pair of sheets of thermoplastic
material which are successively delivered to a forming station.
Twin-sheet thermoforming apparatus of the type disclosed in the
present assignee's U.S. Pat. No. 3,583,036, granted June 18. 1971,
includes sheet supporting carriages which support the sheets to be
joined in superposed relation as they move between a heating
station and a forming station.
In another type of two-sheet thermoforming machine, such as that
disclosed in the present assignee's copending patent application
Ser. No. 268,883, now U.S. Pat. No. 3,787,158, filed in the U.S.
Patent Office on July 3, 1972, the plastic sheets are concurrently
moved in opposite directions and at different levels toward and
away from a forming station.
An object of the present invention is to provide a twin-sheet,
differential pressure thermoforming machine wherein heat fusible,
deformable, thermoplastic sheets may be successively delivered in a
common plane path to a forming station where a configuration is
molded in at least on of the sheets and the sheets are thereafter
fused together to form an object.
Another object of the present invention is to provide twin-sheet
thermoforming apparatus of the character described which includes a
sheet supply system for serially supplying deformable, synthetic
plastic sheets in a common plane circuit to the forming
station,
Still another object of the present invention is to provide
differential pressure, twin-sheet thermoforming apparatus having a
load-unload station at which a pair of sheets used to form an
object are successively loaded on carriages successively moving
past the station, and at which an object formed in the sheets is
subsequently removed from one of the carriages at the load-unload
station.
Another object of the present invention is to provide double-sheet,
differential pressure forming methods and apparatus for
successively moving deformable sheets to a forming station, then
moving one of the sheets out of the path of travel to a position
juxtaposed with a following sheet when it is moved to the forming
station, and then fusing the sheets together to form the
object.
Machines of the type disclosed in the aforementioned patent and
patent application are capable of forming objects in pairs of
plastic sheets of differing thicknesses. The thicker sheets must be
subjected to heat, from a given heating source, for a longer period
of time than the thinner sheets. If the thinner sheets are
subjected to the same heat as that required to prepare the thicker
sheets, the thinner sheets will lose their strength and excessively
sag. In the apparatus disclosed in the referenced patent, the upper
and lower sheets must be maintained at the heating station for the
same length of time. Thus, the heating of one sheet is always
related to the heating of another sheet. It is a further object of
the present invention to provide double-sheet differential pressure
forming apparatus for serially moving sheets from a heating station
to a forming station and heating the sheets independently of each
other.
Other objects and advantages of the present invention will become
apparent to those of ordinary skill in the art as the description
thereof proceeds.
SUMMARY OF THE INVENTION
Apparatus for fabricating a hollow object from a pair of
deformable, thermoplastic sheets comprising the steps of: frame
means with a heating station and a forming station downstream of
the heating station; carrier means for serially moving first and
second deformable, thermoplastic sheets from the heating station to
the forming station; means for heating the first and second sheets
at the heating station; and means for moving the first sheet away
from the carrier means when the first sheet is at the forming
station to a position in which it will be juxtaposed with the
second sheet when the latter is moved to the forming station, for
applying a differential pressure to opposite sides of at least one
of the sheets to form a shape therein, and for clamping the
juxtaposed sheets together to fuse the sheets and form the
object.
The present invention may more readily be understood by reference
to the accompanying drawings, in which:
FIG. 1 is a top plan view of a rotary thermoforming machine
constructed according to the present invention, part of the sheet
heating apparatus being broken away to illustrate the underlying
carriage;
FIG. 2 is a partly sectional, front elevational view, taken on the
line 2--2 of FIG. 1, part of the machine being broken away to more
clearly illustrate a portion of the sheet heating apparatus;
FIG. 3 is a transverse sectional view, taken on the line 3--3 of
FIG. 1;
FIG. 4 is an enlarged, vertical sectonal view, taken on the line
4--4 of FIG. 1, particularly illustrating an upper mold in a raised
removed position and a lower mold in a raised sheet-engaging
position, forming a shape in a sheet at the forming station;
FIG. 4A is a fragmentary top plan view of a platen locking
cylinder, taken along the line 4A--4A of FIG. 4;
FIG. 5 is a view similar to FIG. 4, showing the lower mold carrying
a previously molded sheet in a lowered dwell position and the upper
mold in a lowered forming position, molding a shape in another
sheet of plastic which has been subsequently indexed to the forming
station;
FIG. 6 is an enlarged vertical, sectional view similar to FIG. 5,
illustrating the upper and lower molds in closed position, the
lower mold being illustrated in a position elevated with respect to
the lower mold support platen, in which the upper and lower sheets
are fused together; and
FIGS. 7 and 7A, taken together, comprise a schematic diagram of a
typical electrical control circuit for controlling the operation of
the various elements of the machine illustrated in FIGS. 1-6.
Referring now more particularly to the accompanying drawings, and
in the first instance particularly to FIG. 1, a rotary plastic
sheet supporting carrier or turntable C is mounted for rotary,
indexing movement on a fragmentarily illustrated, stationary frame
F by a central shaft 10 journaled in the frame F in the usual
manner. The turntable C includes a circular, spoked disc F' having
radial spokes 10a fixed to the central shaft 10 and mounting an
annular rim 10b. The turntable C mounts four circuitously arranged
sheet supporting, clamp frame assemblies, generally designated 16,
for gripping the edges of deformable webs or sheets of synthetic
plastic, thermoplastic sheets P1, P2, P3 and P4 which may be on the
order of 36 to 48 inches in size. The sheets P2 and P4 are lighter
gauge sheets which typically may be 0.200 inches thick, and the
sheets P1 and P3 are heavier gauge material, on the order of, for
example, 0.250 inches in thickness. The clamp frame assemblies,
generally designated 16, are of the same character as the clamp
frame assemblies disclosed in the aforementioned patent except that
they are used in inverted position, and they each clamp a single
sheet or web of synthetic plastic material instead of a pair of
such sheets. The clamp frame assembly 16 will not be described in
detail in view of their full disclosure in the aforementioned
patent. As usual, however, they comprise a pair of juxtaposed
frames 23 and 24 (see FIG. 4). Each of the frames 24 is made up of
four separate sections in rectangular formation which are pivotally
mounted to swing downwardly and outwardly to release the plastic
sheet held therein upon retraction of the piston rods 25 of a
plurality of conventional, double acting, fluid pressure operated
clamp cylinders 26.
Suitable synthetic plastic sheets which may be thermoformed in a
manner to be described, are polystyrene, polyethylene and
polypropylene, but it is contemplated that various thermoplastic
materials may be thermoformed in the manner indicated and then
assembled to form parts which consist of upper and lower sheets
thermoformed to desired configurations. The apparatus constructed
according to the present invention is particularly useful for
forming large size containers of various types in various
industries, such as holding tanks for the recreational vehicle
industry, and may be also used to form such diverse products as
hollow, plastic shutters and pallets.
Provided on the frame F is a loading-unloading station, generally
designated 11, first and second sheet heatng stations, generaly
designated 12 and 13, and a forming and assembly station, generally
designated 14. A frame supported, double acting, solenoid actuated,
spring returned, cylinder 9 is provided for indexing the turntable
C to successively move the sheets P1 - P4 to the various stations.
The clamped sheets P1 - P4 are successively incrementally indexed
by the turntable C from the loading-unloading station, generally
designated 11, between vertically spaced banks of heaters 15 and
15a at the first and second sheet heating stations 12 and 13,
respectively, and then to a position between upper and lower molds
19 and 20 at the forming station 14. Conventional geneva or other
apparatus couples the piston rod 9' of cylinder 9 to the turntable
disc shaft 10 to index the turntable 90.degree. each time the
piston rod is extended.
At the loading-unloading station 11, a sheet supply carrier or
table 27 is acutated by the piston rod 28 of a conventional
single-acting, solenoid actuated, spring returned fluid pressure
operated cylinder 29 for vertical movement between a lowered, sheet
receiving position and a raised, sheet discharging position
adjacent a sheet clamp frame assembly 16. Frame supported,
vertically disposed sheet guide rods 30 are provided so that the
plastic sheet becomes automatically centered in proper position on
the table 27 when the table 27 is in lowered position beneath the
level of the guides 30 and the operator places the plastic sheet
thereon.
In FIG. 2, the frame clamp bars 24 are shown swung to a plastic
sheet releasing position so as to receive the sheet P1 which is
being raised into position to be clamped by the clamp frame 16 at
the loading-unloading station 11 (see FIG. 2). The operator
alternately supplies sheets of thin and heavier gauge, for exampe,
on the order of 0.200 thousandths and 0.250 thousandths,
respectively, for a purpose which will later become apparent. When
the table 27 is raised to its uppermost position in which the
plastic sheet engages the upper frame part 23 of the clamp frame
assembly 16, a limit switch LS-12 is tripped and the cylinders 26
are actuated to pivot the clamp frame elements 24 and clamp the
sheet P1 between upper and lower frame parts 23 and 24,
respectively, in the manner indicated in FIG. 4.
At the heatinng station 12, conventional resistance type, elongate
heating elements 15 are supported on the frame F by frame structure
17 and 18 above and below the rotary path of the four clamp frame
assemblies 16. The heater elements 15 comprise quartz tubes of the
type manufactured by E. L. Weigand Company of New Jersey, or
General Electric Company. The quartz heaters 15 are "flashed" for a
very short period, i.e., 10 seconds, when the thin sheets P2 and P4
are at the first heating station 12 and are maintained energized
for a longer period when thicker sheets P1 and P3 are at the first
heating station 12. At the heating station 13, conventional
infra-red type, elongate heating elements 15a are supported on the
frame F by frame structure 17a and 18a. The infra-red heaters 15a
are intermittently operated for a portion of the total time the
sheets are at the second heating station 13.
At the forming station 14, upper and lower mold members 19 and 20,
respectively (see FIG. 4), are mounted so as to be vertically moved
by conventional, double acting, fluid pressure operated cylinders
21 and 22, respectively. The lower mold raising cylinder 22 is
solenoid actuated on both the upstroke and return, but the upper
mold lowering cylinder 21 is solenoid actuated to the extend
position and is spring returned to the retracted or raised
position.
As FIGS. 4 and 5 both particulalry indicate, the upper and lower
molds 19 and 20 are provided with vacuum manifolds 31 and 32,
respectively, which communicate respectively with vacuum source
lines 33 and 34. The mold cavities 35 and 36 of molds 19 and 20,
respectively, are provided with ports 37 communicating with the
manifolds 31 and 32, respectively. As particularly indicated in
FIG. 4, the upper mold 19 is supported on an upper platen,
generally designated 38, which incldes side rails 38a, spanned by
platen brace rods 38c and channel plates 38b. The channel plates
38b are sandwiched between a mold plate 38a, fixed to the upper
mold 19, and a mold plate 38d fixed to the piston rod 21a of the
cylinder 21. The upper platen 38 mounts guide rods 39 that are
received in cushioning clinders 40 secured to the frame structure
F. The upper platen 38 supports fixed nuts 42, which threadedly
receive lock shafts 43, having locking lugs 44 at their lower ends.
As FIG. 1 particularly indicates, four such lock shafts 43 are
provided and are revolved 90.degree. in unison by collars 45 which
are fixed thereto to achieve a locking operation in a manner which
will be described.
A pair of lugs or ears 46 and 47 (FIG. 1) are fixed to each collar
45. A solenoid controlled, double acting, fluid pressure operated
cylinder 48 is provided on the upper platen 38 for rotating the
vertical platen locking shafts 43 in unison via a linkage system
including a link 49 pivotally connected at its ends to the ears 47
of the collars 45 at the right end of the assembly in FIG. 1, and a
link 50 pivotally connected at its ends to the ears 46 of the
radially outermost collars 45. Finally, a link 51 is also pivotally
connected at its ends to the ears 47 on the collars 45 at the left
end of the mold station as viewed in FIG. 1.
As FIG. 4 also indicates, the lower mold 20 is supported by a lower
platen, generally designated 52, which includes side frame members
53, spanned by brace rods 53c, supporting fixed nuts 53a that
receive vertical, threaded rods 54 having heads 55 provided with
key-hole openings 55a for receiving the platen locking shafts 43
and lugs 44. The inner ends of the key-hole openings include offset
portions 55b (FIG. 4) which receive the logs 44 when the lock
shafts 43 are revolved 90.degree. to lock the platens together.
The lower platen 52 includes a cross bar 52f mounted on the piston
rod 22a of the lower fluid pressure operated clinder 22 and carries
guide rods 56 which are received in cushioning cylinders 40 fixed
to the frame structure F. Spanning the side rails 53 of the lower
platen 52 is a lower pressure plate 57 which, at its four corners,
mounts vertical guide rods or pins 58 which are freely and slidably
received in openings 59 provided in an upper pressure plate 60. The
upper pressure plate 60 is connected to the underside of the lower
mold 20 via channel plates 61 and a manifold plate 62.
Apparatus is provided for moving the lower mold 20 upwardly
relative to the lower platen 52, when the sheets are clamped
between the molds 19 and 20, and includes a series of individual
hose-like, air-expansible bladders 63, provided between the
relatively movable pressure plates 57 and 60. Plainly, when air is
admitted to the bladders 63, the pressure plate 60 and lower mold
20 will immediately be forced upwardly to pinch the upper and lower
sheets clamped between the molds 19 and 20 at the forming station
to a reduced thickness (see FIG. 6). It is to be understood that
the bladders 63 are formed of a flexible, collapsible material such
as a resilient fabric, which normally is in the semi-collapsed
condition shown in FIG. 4. Rigid end plates 63a are provided for
the inflatable tubes 63 and their air pressure supply tubes 64 lead
into one end of each expansible tube 63 through a rigid end plate
63a, as shown in FIG. 3. Individual valves 65 for the tubes 64
permit each of the tubes 63 to be shut down, if desired, when they
are not necessary to the mold raising operation and there is no
need for air from a manifold 66 to be communicated to them via
their supply tube 64.
To insure that the sheet supporting carriages 16 are halted in the
identical position at the forming station each time the turntable C
is indexed, apparatus for locking the turntable C in the various
fully indexed position is provided and comprises a rim lock 70
pivotally mounted on a frame supported shaft 72 for movement
between the unlocked position, illustrated in FIG. 1, and a rim
engaging position received in any one of a plurality of recesses 77
provided in the rim 10b of the turntable C. To swing the lock 70, a
solenoid actuated, spring returned, fluid pressure operated control
cylinder 74 is provided including a piston rod 75 coupled to the
pivoted rim lock 70. A limit switch LS-9 is tripped by the rim lock
70 in the unlocked position.
A plurality of limit switches are provided for controlling the
operation of the machine and include a pair of limit switches LS-3
and LS-4 mounted 90.degree. apart on the frame F in position to be
alternately tripped by a pair of 180.degree. spaced paddles 76
fixed to the turntable shaft 10.
The upper mold 19 includes a molding pressure needle 84 which is
movable through an aperture 84a in the mold sidewall to pierce a
sheet of plastic drawn into the upper mold cavity 35 and introduce
pressurized air into the deformed sheet for assisting it into
intimate conformity with the upper mold cavity 35.
Top and bottom "platen extend" limit switches LS-5 and LS-6 (FIG.
4) are supported on the frame to be tripped by the upper and lower
molds 19 and 20, respectively, in their closed molding positions,
illustrated in FIG. 3. A platen lock limit switch LS-7 is mounted
on the upper platen 38 to be tripped when the lock 44 moves to
platen locking position. A rim lock open limit switch LS-9 is
mounted on the frame F in position to be tripped when the rim lock
70 is retracted from the rim 10b. A platen unlock limit switch
LS-10 is mounted on the upper platen 38 in position to be tripped
when the platen locks 44 move to a platen unlocking position
aligned with the key-hole 55b in the heads 55 supported on the
lower platen 53.
A "bottom platen extend" limit switch LS-11 (FIG. 4) is mounted on
the frame F in position to be tripped when the bottom mold 20 is
moved to the molding position illustrated in FIG. 3. A load table
extend limit switch LS-12 is mounted on the frame F at the load
station 11 in position to be tripped when the sheet supply or load
table 27 is extended from the position illustrated in FIG. 2 to a
raised position at a clamp frame assembly 16.
A plurality of "clamp frame" limit switches LS-17, LS-18, LS-19 and
LS-20 are supported on the turntable C in position to be tripped
when the sheets P1 - P4, respectively, reach the forming station
14. Apparatus for tripping the llimit switches LS-17 through LS-20
comprises a cylinder 91, at the forming station 14, having a piston
rod 92 which extends into the path of the limit switches LS-17 and
LS-20. The limit switches LS-17 through LS-20 are also successively
tripped at the load-unload station 11 by the piston rod 94 of a
double acting, solenoid actuated, fluid pressure operated cylinder
93 which is selectively energized. A sheet supply control limit
switch LS-21 is mounted in the turntable C in position to be
tripped when the frame 16 opens at the load-unload station.
THE CONTROL CIRCUIT
The control circuit for controlling the apparatus previously
described is schematically illustrated in FIGS. 7 and 7A, and
includes a pair of electrical supply lines L1 and L2 connected
across a supply of electrical power such as 110 volt, 60 cycle,
altenating current and a plurality of circuit and sub-circuit lines
designated L3 through L37, respectively. Connected in line L3
across the lines L1 and L2 are the normally open relay contacts
5CR1, which are closed when a relay 5CR (line L5) is energized, and
a control relay 3CR which, when energized, opens a pair of normally
closed contacts 3CR1 (line L26) and closes a pair of normally open
contacts 3CR2 (line L28). Connected in line L4 across the lines L1
and L2 are the normally closed limit switch contacts LS-3a which
are opened when the frame supported limit switch LS-3 is tripped by
a paddle 76 on the turntable shaft 10, as is illustrated in FIG. 4.
Connected is series with the limit switch contacts LS-3a (line L4)
are the normally open timer contacts T1A which close as a timer T1
(line L8) times out, and a rim lock solenoid 74a for moving the
piston rod 75 of the rim lock cylinder 74 in such a manner as to
move the rim lock 75 to locking position in one of the recesses 77
in the turntable rim 10b. The junction 80a (line L3) of the timer
contacts T1A and the rim lock solenoid 74a is also connected to the
control relay 3CR via a line 80. Connected in line L5, across the
lines L1 and L2, is a set of normally closed limit switch contacts
LS-4a which are opened and closed alternately with the contacts
LS-3a by the turntable supported paddles 76. Also serially
connected in line L5 is a set of normally open timer contacts T4A
which close as a timer T4 (line L10) times out, and a holding relay
5CR which, when energized, is operative to close the normally open
contacts 5CR1 (line L3).
Connected between the junction 81 (line L4) of limit switch
contacts LS-3a and timer contacts T1A (line L4) and the line L2 is
a plurality of parallel circuits including lines L6, L8, L9, L9A
and line L10A. Line L6 includes the normally open timer contacts
T1B which close as the timer T1 (line L8) times out and the
normally open limit switch contacts LS-5a, which close when the
frame supported limit switch LS-5 is tripped by the upper mold 19
in the fully extended, molding position at the sheet line. Also
connected in line L6 is a set of normally open limit switch
contacts LS-6a which are closed when the frame supported limit
switch LS-6 is tripped by the lower mold 20 in the fully extended
position at the sheet line, as is illustrated in FIG. 3. The line
L6 also includes the platen lock control solenoid 48a which, when
energized, actuates the platen lock control cylinder 48 in such a
manner as to rotate the platen lock shafts 43 about their axes to
lock the platens 38 and 52 together. Connected in parallel with the
platen lock solenoid 48a is a holding relay 1TDR (line L6A) which,
when energized, closes a set of normally open holding contacts
1TDR1 (line L22).
Connected in line L7 between the junction 82 (line L6) of timer
contacts T1B and limit switch contacts LS-5a (line L6) and the line
L2 is a set of normally open limit switch contacts LS-7a which
close when the upper platen supported limit switch LS-7 is tripped
by the lock shafts 43 and locking lugs 44 moving to the platen
locking positions. Connected in series with the limit switch
contacts LS-7a (line L7) are the normally open timer contacts T1C
which close as the timer T1 (line L8) times out, and a "sheet
pinching" solenoid 65a for operating the valve which supplies
pressurized air via the tube 66 to the air expansible bellows or
bladders 63. This forces the lower mold 20 upwardly, relative to
the lower platen 52, toward the mold 19 to pinch the double
thickness sheets and provide a single thickness perimetrical
portion on the container formed at the forming station 14.
A solenoid 84a (line L7A) for moving the air pressure supplying
needle 84 through the sheet in the upper mold and admitting mold
pressure thereto is connected in parallel with the solenoid 65a. A
pressure responsive switch 86 is connected in series with the
solenoid 84 and is set at a pressure of 40 p.s.i., for example,
which will interrupt mold pressure and withdraw the needle when the
predetermined pressure is reached in the upper mold cavity 35.
Connected in lines L8 and L9 are the vacuum control timer T1 and
pressure forming control timer T2, respectively. The timer T1, when
energized, sequentially closes the timer contacts T1A (line L4),
T1B (line L6), T1C (line L7), T1D (line L11), T1E (line L12). The
timer T2, when energized, sequentially closes the normally open
timer contacts T2A (line L23), T2B (line L25), and T2C (line L26).
The specific sequence of timer contact closing will be more
particularly described hereinafter. Connected in line 9A between
the junction 81 and line L2 is a timer T9 including normally open
timer contacts T9A (line L14) which close as the timer T9 times
out. Also connected between the junction 81 (line L4) and the line
L2 is a timer T10 (line L10A) which closes the normally open timer
contacts T10A (line L16) as it times out.
Connected between the junction 87 (line L5) of LS-4normally closed
limit switch contacts Ls-4a (line L5) and timer contacts T4A and
line L2 is a circuit line L10, including a timer T4 which
sequentially closes the normally open timer contacts T4A (line L5),
T4B (line L13), T4C (line L15), T4D (line L17), T4E (line L24), T4F
(line L27) and T4G (line L29). The sequence of timer contact
closing will be more particularly described hereinafter.
Connected in line L11, across the lines L1 and L2, are the normally
open timer contacts T1D and a vacuum control solenoid 33A for
communicating forming vacuum to the upper mold 19. Connected in
line L12, across the lines L1 and L2, are the normally open timer
contacts T1E and the lower vacuum control solenoid 34a for
introducing forming vacuum to the lower mold 20.
Connected in line L13, in parallel with the timer contacts T1E, are
the normally open timer contacts T4B. Connected in line L14, across
the lines L1 and L2, are the normally closed, manually operated,
toggle switch TS-1, the normally open timer contacts T9A, which
close as the timer T9 (line L9A) times out, and a top heater
control relay 1CR which, when energized, operates the top heaters
15 at the first heating station 12. Connected in parallel with
timer contacts T9A (line L14) are the timer contacts T4C which
close as the timer T4 times out to energize the control relay 1CR
(line L14). The timer contacts T4C remain closed for a shorter
period of time than do contacts T9A as will be later described. The
circuit line 16 is connected across the lines L1 and L2 and
includes the control circuitry for the bottom heaters 15 at the
first heater station or oven 12. Connected in line L16 is a set of
normally closed, toggle switch contacts TS-2, the normally open
timer contacts T10A which close as the timer T10 times out, and the
oven control relay 2CR which, when energized, causes the bottom
quartz heaters 15 at the first heating station 11 to be energized.
Connected in line L17 in parallel with the timer contacts T10A is a
set of timer contacts T4D (line L17) which are closed as the timer
T4 times out.
The control circuitry for controlling the top infra-red heaters 15A
at the second heating station or oven 13 is connected in line L18,
across the lines L1 and L2, and comprises a normally closed,
manually operated, toggle switch TS-3 and a timer T7 which opens a
set of normally closed timer contacts T7A (line L19) as the timer
T7 times out. Line L19 is connected in parallel with timer T7 and
includes the timer contacts T7A connected in series with a bottom
heater oven control relay 3CO. When the relay 3CO (line L19) is
energized, the top infra-red heating elements 15A at the second
heating station 13 or oven are energized.
The control circuitry for the bottom heating elements 15a at the
second heating station or over 13 is connected in line L20 across
the lines L1 and L2 and comprises a set of normally closed,
manually operated toggle switch contacts TS-4 and a timer T8
including a set of normally closed contacts T8A (line L21) which
open as the timer T8 times out. The circuit line L21 is connected
in parallel with the timer T8 and includes the timer contacts T8
connected in series with a control relay 4CR for energizing the
bottom heater elements 15A. The timers T1, T2, T3, T4, T5, T6 T9
and T10 are multiple station, settable, linear timers of the type
manufactured by Eagle Manufacturing Company as Model No.
HM5-05-A6-02-06 and include separably energized clutches (not
shown) as usual. The timers T7 and T8 are also multiple station,
linear timers of the same general type, but are settable to
intermittently open and close the contacts T7A and T8A for a
percentage of the total running time of the timer motors. For
example, the timers T7 and T8 typically operate for 120 seconds,
but the contacts T7A might only be closed for 108 seconds or 90
percent of the total timing period.
Circuit line L23 is connected across the lines L1 and L2 and
includes the control circuitry for lowering the upper mold 19 to
the sheet line position and comprises a set of normally closed
limit switch contacts LS-9a, which is opened when the rim lock 70
is in the unlocked position to actuate the limit switch LS-9, the
normally open timer contacts T2A, which close as the forming timer
T2 times out, and an upper mold lowering solenoid 21a which, when
energized, directs fluid to the cylinder 21 in such a direction as
to move the upper mold 19 to the molding position engaging a sheet
on one of the carriages 16. Connected between the junction of the
timer contacts T2A (line L23) and the upper mold lowering solenoid
21a and the line L1 is a circuit line L22 including the normally
open holding contacts 1TDR1 which are closed when the holding relay
1TDR (line L6A) is closed.
Connected between a junction 90 (line L23) of the limit switch
contacts LS-9a and the timer contacts T2A and the line L2 are
circuit lines L25 and L26. Circuit line L25 includes the control
circuitry for raising the lower mold 20 and comprises the normally
open timer contacts T2B which close as the forming timer T2 (line
L9) times out, after a shape is molded in one of the thicker
sheets, and a solenoid 22a for moving the lower mold 20 upwardly to
the mold position illustrated in FIG. 3. Connected in parallel with
the timer contacts T2B (line L25) is a set of timer contacts T4E
(line L24) which close as the timer T4 (line L10) times out after a
shape is molded in one of the thinner sheets.
The circuit for retracting the lower mold 19 is connected in the
circuit line L26, across the lines L1 and L2 and includes the
normally closed relay contacts 3CR1, which are opened when the
relay 3CR (line L3) is energized, the normally open timer contacts
T2C which close as the thicker sheet, forming timer T2 times out,
the normally closed limit switch contacts LS-10a, which are closed
as the platen locks 44 are unlocked to trip the limit switch LS-10,
and the lowering solenoid 22b for directing fluid to the cylinder
22 to move the lower mold 20 to the lowered position illustrated in
FIG. 5. Connected in line L27, in parallel with the contacts 3CR1
and T2C (line L26), is the set of timer contacts T4F which are
closed as the thin sheet timer T4 times out. As will be described
more particularly hereinafter, the timer contacts T4E and T4F for
the thin sheet timer T4 are closed for a substantially shorter
period than the timer contacts T2B and T2C for the thick sheet
timer T2 so that the lower mold 20 will dwell at the sheet line
position for a longer period when a thick sheet is being formed.
Connected between the line L1 and the junction of the timer
contacts T2C (line L25) and the limit switch contacts LS-10a is a
set of normally open holding contacts 3CR2 which close when the
holding relay 3CR (line L3) is energized.
The control circuit for energizing the turntable indexing cylinder
9 is connected in line L9, across the lines L1 and L2, and includes
a set of normally open limit switch contacts LS-9a which close when
the rim lock 70 is unlocked to trip the limit switch LS-9, and a
solenoid 9A for directing fluid to the turntable indexing cylinder
9, to rapidly accelerate the turntable C. A line L33 is connected
across the solenoid 9A and includes the normally open limit switch
contacts LS-16a, which close when a frame supported limit switch
LS-16 is tripped midway through the stroke of the piston rod 9',
and a solenoid R which, when energized, interrupts the supply of
air to the cylinder 9 so that the piston rod 9' is permitted to
"coast" to its fully extended position so that the turntable is not
abruptly halted at the end of the piston rod stroke.
A pair of conventional current carrying brushes, schematically
designated 94 and 95 (FIg. 7) are connected to the lines L1 and L2
respectively, and engage a pair of slip rings, schematically
designated 96 and 97 respectively, connected to a pair of circuit
lines L1' and L2' on the turntable C.
Connected across the lines L1' and L2' are circuit lines L34 - L37
for controlling the opening and closing of the clamp frame
assemblies 16 supporting the sheets P1 - P4. Connected in the
circuit line L34, are a set of normally open limit switch contacts
LS-17a, which close when the turntable supported limit switch LS-17
is tripped, and a solenoid 26A which actuates the solenoid
actuated, spring returned, clamping frame cylinders 26 on the
carriage 16 carrying the sheet P4 to release the sheet P4.
Connected in lines L35 is a set of normally open limit switch
contacts LS-18a which close when the turntable supported limit
switch LS-18 is tripped, and a solenoid 26B which energizes the
clamping frame solenoids 26 to retract the frame members 24 and 25
gripping the sheet P3 and release the sheet P3. Connected in line
L36 is a set of normally open limit switch contacts LS-19a, which
close when the turntable supported limit switch LS-19 is tripped,
and the solenoid 26C for energizing the solenoid actuated, spring
returned, clamp frame cylinders 26 on the carriage which supports
the sheet P2 to release the sheet P2. Connected in line L37 is a
set of limit switch contacts LS-20a, which are closed when the
turntable supported limit switch LS-20 is tripped, and a solenoid
26D which, when energized, retracts the clamping frame member 24
and 25 which support the sheet P1 to release the sheet.
Circuit lnes L29, L30, and L31 are connected in parallel across the
line L1 and L2 and control the actuation of the limit switches
LS-17 through LS-20 at the forming and load-unload stations as will
presently be described. A solenoid actuated, spring returned, fluid
operated cylinder 91 is mounted on the frame F at the forming
station 14 and includes a piston rod 92 which is extendable to trip
the turntable supported limit switches LS-17 and LS-19 to release
the thin sheets P2 and P4 at the forming station after a shape is
formed therein. A double acting, solenoid controlled, fluid
pressure operated cylinder 93 is mounted on the frame F at the
load-unload station 11 and includes a piston rod 94 extendable to
trip the turntable supported limit switches LS-17 through LS-20 at
the load-unload station 11. This will open the clamp frame
assemblies 16 to release sheets having objects formed therein and
prepare the carriage clamp frame assemblies 16 to receive other
sheets.
Circuit line L29 includes the normally open timer contact T4G, a
set of normally open limit switch contacts LS-11a, which close when
a limit switch LS-11 at the forming station 14 is tripped by the
lower mold 20 at the forming position, and a solenoid 91a which,
when actuated, causes the piston rod 92 of the cylinder 91 to be
extended.
Connected in line L30 is a set of normally open limit switch
contacts LS-13a, which close when the upper mold 19 extends to mold
position to trip the frame supported limit switch LS-13 at the
forming station 14, the normally closed limit switch contacts 93b1,
which open when a solenoid 93b (line L31) is energized, and a clamp
frame opening solenoid 93a for extending the piston rod 94 of the
cylinder 93. Connected in line L31 is a set of normally open limit
switch contacts LS-12a of a limit switch LS-12, which is tripped
when the load table 27 is upwardly extended at the sheet
load-unload station 11, and the clamp frame close solenoid 93b for
retracting the piston rod 94 of cylinder 93 so that the clamp frame
assemblies can be closed at the load-unload station 11.
Circuit line L33A includes a set of normally open limit switch
contacts LS-21a, which are closed when a frame supported limit
switch is tripped by the frame assemblies 16 opening at the
load-unload station 11, connected in series with a solenoid 29a
which, when energized, actuates the solenoid actuated, spring
returned, fluid pressure operated sheet supply table raising
cylinder 29.
THE OPERATION
It will be assumed that the machine is in the midst of its
continuous cycle and a sheet P1 is clamped in the clamp frame 16 at
the loading-unloading station 11, a sheet P2 is clamped in the
clamp frame assembly 16 between the heaters 15 at the oven or
heating station 12, a sheet P3 is clamped in a sheet clamp frame
assembly 16 at the oven or heating station 13, and a sheet P4 is
clamped in a sheet clamp frame 16 at the forming station 14.
Shapes are molded in the lighter gauge sheets P4 and P2 by the
lower mold 20, and the shapes are molded in the heavier gauge
sheets P1 and P3 by the upper mold 19 as will presently be
described. At the time the sheet P4 is initially delivered to the
forming station 14, the upper and lower molds 19 and 20 are in the
spread, chain line positions, illustrated in FIG. 2. The limit
switch LS-3 will have been actuated by one of the paddles 76, as
illustrated in FIG. 1, to open the limit switch contacts LS-3a
(line L4) while the limit switch contacts Ls-4a (line L5) remain
closed to energize the timer T4 (line L10). As the timer T4 times
out, the contacts T4E (line L24) will close to energize the lower
platen raising solenoid 22a (line L25) for raising the lower platen
52 and lower mold 20 upwardly to the sheet line position,
illustrated in FIG. 4, engaging the sheet P4.
The timer contacts T4B (line L13) are set to close at the time the
mold 20 engages the sheet P4 to energize the solenoid 34a (line
L12) which communicates vacuum to the lower mold cavity 32 to draw
the sheet P4 into the lower mold cavity 36 via the suction forces.
The timer contacts T4G (line L29) close and the clamp frame opening
solenoid 91a (line L29) is energized, via the limit switch contacts
LS-11a which were closed when the limit switch LS-11 was tripped by
the lower platen 52 being moved to the raised position. When the
clamp frame opening solenoid 91a is energized, the cylinder 91, at
the forming station 14, is actuated to extend the piston 92 into
the path of the limit switch LS-17 and closed the contacts LS-17a
(line L34) energizing the solenoid 26a (line L34) which actuates
the clamp cylinders 26 on the sheet frame assembly 16 supporting
the plastic sheet P4. This releases the sheet P4 for downward
movement with the lower mold 20. The lower mold 20 is lowered to
the lowered position illustrated in chain lines in FIG. 4, when the
timer contacts T4F (line L27) close to energize the solenoid 22b
(line L26).
When the lower mold 20 is extended to the raised position, it also
trips the frame supported limit switch LS-6 to close the limit
switch contacts LS-6a (line Ll16) and energize, when the timer
contacts T4D (line L17) close, the bottom heater oven control relay
2CR. As soon as the bottom mold 20 is retracted, i.e., 10 seconds
later, the limit switch LS-6 is deactuated to open the contacts
LS-6b and interrupt the relay 2CR (line L16) so that the quartz
heaters substantially provide "flash" heat only to the light gauge
sheet P2 at the first heating station 12. The heavy gauge sheet P3
at the heating station 13 is heated by the heaters 15a which are
energized through the control relay 3CR (line L19) that is
intermittently energized through the percentage timer control
contacts T7A. Although the heaters 15a are intermittently turned on
and off, the heating time is sufficient so that the temperature at
the second station 13 does not substantially fluctuate but rather,
remains substantially constant.
When the solenoid 22b (line L26) is energized and the lower mold 20
carrying the sheet P4 has been lowered, as mentioned, the timer
contacts T4A (line L5) close to energize the relay 5CR (line L5)
which closes the contacts 5CR1 (line L3) to energize the rim lock
solenoid 74a (line L4) and retract the rim lock arm 70. This
actuates the limit switch LS-9 thereby closing the contacts LS-9a
(line L33) to energize the turntable rotate solenoid 9A which
indexes the turntable C and moves the sheet P3 into the forming
station 14 superposed with the now lowered sheet P4. When the
turntable indexing rod 9' extends, the limit switch LS-16 is
actuated to open the contacts LS-16a and bleed the air pressure off
the turntable indexing cylinder 9 so that the piston rod 9 does not
abruptly halt, but coasts to its fully extended position.
When the turntable has been indexed 90.degree., the limit switch
LS-4 is deactuated and the limit switch LS-3 is tripped by one of
the turntable supported paddles 76 (FIG. 1) to concurrently
energize the timers T1, (line L8), T2 (line L9), T9 (line L9A), and
T10 (line L10A). The lower mold 20 temporarily dwells in the
lowered position, and the upper platen 38 and upper mold 19 are
lowered when the timer contacts T2A (line L23) close to energize
the top platen lowering solenoid 21a (line L23) which directs
pressurized fluid to the cylinder 21 in such a manner as to move
the upper mold 19 to the molding position illustrated in FIG. 3.
The timer contacts T1D (line L11) then close to energize the top
vacuum control solenoid 33a for introducing vacuum to the upper
cavity 31 and mold 19 to form a shape in the sheet P3. At the same
time, the timer contacts T2B (line L25) close to energize the lower
platen, raising solenoid 22b which moves the lower platen 52 and
the lower mold 20 to the raised molding position so that the lower
sheet P4 is engaged by the superposed sheet P3. At the time the
sheets P4 and P3 are engaged, the limit switches LS-5 and LS-6 are
tripped to close the limit switch contacts LS-5a and LS-6a (line
L6). When the lower mold 20 is moved to raised position, the lock
shafts 43 and lugs 44 on the upper platen 39 are received in head
members 55 on the lower platen 52. When the timer contacts T1B
(line L6) close, the platen lock solenoid 48a (line L6) will be
energized to actuate the platen lock cylinder 48 and revolve the
shafts 43 and the platen locks 44 90.degree. to their locking
positions received in the offset slot portions 55b. This provides a
positive lock, positively preventing separation of the upper and
lower platens 38 and 52, respectively. The locking of the platens
is signalled by the actuation of limit switch LS-7 which closes the
limit switch contacts LS-7a (line L7). When the timer contacts T1C
(line L7) close, the "pressure squeeze" solenoid 65a is energized
to actuate the valve 65 which communicates pressurized air to line
66 so that the hoses or expandable air bladders 63, on the lower
platen 52, are expanded to the positions illustrated in FIG. 6.
This raises the lower mold 20 relative to the platens and tightly
squeezes the sheets P4 and P3 around their edges so as to pinch the
sheets and reduce the combined thickness of the sheets to the point
where a good bond is achieved. The upper and lower molds 19 and 20
remain in the operative positions until the formed object cools.
The molds 19 and 20 are then returned to their retracted positions
away from the part which is held by the carriage 16 clamping the
sheet P3 as will presently be described.
When the limit switch contacts LS-3a (line L4) close, the timers T9
(line L9A) and T10 (line L10A) are energized to close the contacts
T9A (line L14) and T10A (line L16) to energize the heater oven
control relays 1CR (line L14) and 2CR (line L16) so that the sheet
P1 which was indexed to the first heating station or oven 12, is
heated by the upper heaters 15 at the first oven 12. The sheet P1,
now at the first heating station 12, is a heavy gauge sheet so the
contacts T9A (line L14) and T10A (line L16) remain closed for a
substantially longer period than the timer contacts T4C (line L15)
and T4C (line L17) were closed so that the heavier gauge sheet P1
will be heated by both upper and lower heaters 15 for a relatively
lower period of time than the lighter gauge sheet P2 was previously
heated by the second oven 12. The light gauge plastic sheet P2,
which is now indexed to the second heating station 13, is also
heated by the heaters 15a that are intermittently energized as
previously described to maintain a substantially constant
temperature at the station 13.
More particularly, when the top platen 58 is extended, the timer T8
(line L20) is energized to intermittently open and close the
contacts T8A to energize the relay 4CR which selectively controls
the energization of the lower heaters at the second oven 13. The
temperature at the oven or heating station 13 can be controlled by
adjusting the timer T7 and regulate the percentage of the timer
operating time that the contacts T7A and T7B are closed. Although
the heaters 15a at the second oven are intermittently energized,
the heat does not substantially fluctuate. The lighter gauge sheets
P2 and P4, which are "flash" heated only by the heaters 15 at the
first heating station 12, are heated for a longer period of time by
both top and bottom heaters at the second station 12.
A typical cycle time to complete the formation of the part at
forming station 14 is 4 minutes. Once the part has been assembled
and the carrier C is indexed, the operator at station 11 must
unload the completed part and reload a heavier gauge sheet in 10
seconds. Thus, while the parts may typically be heated for 4
minutes, the two sheets which are assembled to make a part are in
the heater units a total of 4 minutes and 10 seconds. Neither will
be heated during the entire length of time. The thinner gauge sheet
obviously will be heated for a lesser period of time than the
thicker gauge sheet. About three minutes heating time is required
for the thicker gauge sheet, and about two minutes heating time is
required for the thinner gauge sheet, and this is accomplished by
delaying the turning on of the quartz tubes 15 with the timers T7
and T8.
When the turntable C was rotated 90.degree. to move the heavier
gauge sheet P3 to the forming station 14, the carriage 16, which
previously supported sheet P4, was moved to the load station 11 to
actuate the limit switch LS-13 and close the limit switch contacts
LS-13a (line L30) to energize the clamp frame opening solenoid 93a
which actuates the unclamp cylinder 93 at the load-unload station
11. This extends the piston 94 into the path of the limit switch
LS-17 to close the limit switch contacts LS-17a (line L34). This
energizes the solenoid 26A (line L34), causing the clamp frame
assembly 16 previously supporting the sheet P4, to be opened. When
the clamp frame assembly 16 is opened at the load station, the
limit switch LS-21 (FIG. 2) is tripped to close the limit switch
contacts LS-21a (line L33a) to energize the table raising solenoid
29a (line L33A) and move the sheet support table 27 upwardly to a
position in which the next sheet is received by the carriage
previously supporting sheet P4. When it reaches the proper
position, the limit switch LS-12 is tripped to close limit switch
contacts LS-12a (line L31) and energize the solenoid 93b. This
causes the piston rod 94 on the cylinder 93 to be retracted and
deactuates the limit switch LS-17a so that the clamp frame solenoid
26a (line L34) can be deenergized and the frame assembly 16
returned to its original clamping position.
After the sheets P4 and P3 are fused together and the hollow part
is formed, the forming cycle is reversed and the timer contacts T1C
(line L7) open to deenergize the pressure squeeze solenoid 84a so
that the air bladders 63 collapse. The timer contacts T1B (line L6)
open to deenergize the platen lock solenoid 48a (line L6)
permitting the platen locking lugs 44 to be disposed in alignment
with the keyhole slot 55a. Also, the timer contacts T1D (line L11)
and T1E (line L12) open to deenergize vacuum control relays 33a and
34a and remove the vacuum from the top and bottom molds. The timer
contacts T2A (line L23) open to deenergize the upper platen
lowering solenoid 21a permitting the upper mold 19 to be
spring-returned to the raised position, and the contacts T2C (line
L26) close to energize the lower mold lowering solenoid 22b.
The lower sheet P4 will be bonded to the upper sheet P3 to be
carried thereby in the clamp frame assembly holding the sheet P3.
If necessary, conventional air ejection devices may be mounted on
the top and bottom molds to assist in removing plastic sheets which
inadvertently stick to the molds. The top sheet with the part
formed therein, separates from the top mold and the bottom sheet P4
separates from the bottom mold to be carried by the clamp frame
assembly holding the sheet P3.
With the part thus formed, the timer contacts T1A time out to
energize the rim lock retract solenoid 74a which retracts the rim
lock 70 to actuate the limit switch LS-9. This closes the limit
switch contacts LS-9A (line L33) and again energizes the turntable
rotating solenoid 9A (line L33). This causes the turntable C to be
indexed 90.degree. so that the formed part is now disposed at the
loading-unloading station. This will trip the limit switch LS-13
causing the contacts LS-13a (line L30) to again close and energize
the clamp frame opening solenoid 93a which opens the clamp frame 16
supporting the part. The operator manually removes the part and at
the same time, the limit switch LS-21 is tripped to cause the next
sheet on the turntable 27 to be raised into position to be clamped
by the clamp frame previously holding the sheet P3. When the sheet
reaches the raised position, the limit swich LS-12 is again tripped
to close the contacts LS-12a (line L31) to energize the clamp frame
solenoid 93b and clamp the sheet on the carriage 16 to be indexed
therewith to the heating station 11. The cycle is then
repeated.
It is to be understood that the drawings and descriptive matter are
in all cases to be interpreted as merely illustrative of the
principles of the invention, rather than as limiting the same in
any way, since it is contemplated that various changes may be made
in various elements to achieve like results without departing from
the spirit of the invention or the scope of the appended
claims.
* * * * *